For almost eight months after launching Stack Overflow to the public, we had no concept of banning or blocking users. Like any new frontier town in the wilderness of the internet, I suppose it was inevitable that we'd be obliged to build a jail at some point. But first we had to come up with so...

I used to carry a lot of that stuff, but now I have cut way back.
What I don't carry anymore:
Shopping cards - What barcode? Just give them your phone number. My wife has signed up for so many of those that I just give them my number and it always works.
Leatherman - Lost a good one when forgetting about it at the airport. Don't carry mine anymore, because I rarely need tools outside the house anyway.
A unique thing I do carry:
Earphones - I carry a set of Sennheiser earphones that wind up into a flat circular case. I can plug them into my Android phone or the computer at work or a plane or wherever. Very useful.
Also:
USB drive - The real question is what is on your USB drive. I have found a ton of great utilities on PortableApps.com and PortableFreeware.com. These are the ones I use regularly:
7-zip - For unzipping. Especially 7z and rar files.
AlternateStreamView - Remove that pesky "this file was downloaded" message.
CDBurnerXP - For computers with burners but no install capability.
CPUZ - Your friend/relative wants a memory upgrade. What should they buy?
EjectUSB - Closes all programs related to the drive and readies it for removal. This is the greatest program ever.
Ethereal - Network sniffer (guess I should update to WireShark)
FileMon - Watch which files a program opens.
FileZilla - FTP
Firefox - duh
Hexplorer - Hex editor
IcoFX - Icon editor
JKDefrag - Defragger
KeePass - Password management
MagicJellybeanKeyfinder - Get Windows install codes for current machine.
OpenOffice - Mostly opening .docx and .xslx for people who don't have MS Office 2007+. Also, it's easy to turn docs into PDFs.
PhotoFiltre - Great image editor. (Old free version.)
ProcessExplorer - TaskManager on steroids.
QueryExpress - Connect to Access, SQL or Oracle databases with no programs or drivers installed. Awesome.
Recuva - Malware uninstaller.
RoadKillUnstoppableCopier - Recover your friends' mangled CDs and DVDs.
SIW - System Information for Windows
TCPOptimizer - Sets the receive window, IE max connections, etc. to optimum values.
WinDirStat - Fastest drive clutter finder.
WinMD5Sum - Great for checking the latest Linux ISO.
WinMerge - Source code diff tool.

Like any self-respecting geek, I'm mostly an indoor enthusiast. But on those unfortunate occasions when I am compelled -- for reasons entirely beyond my control -- to leave the house, I do so fully armed with my crucial utility belt items. Yes, you heard me, I transform from the geeky Bruce Wa...